Endo-1,3(4)-.beta.-glucanases (E.C. no. 3.2.1.6) constitute a group of hydrolases, which catalyse endo hydrolysis of 1,3-.beta.-D-glycosidic linkages in .beta.-1,3-glucans, such as curdlan, lichenan and laminarin, a major component of the cell walls of fungal (including yeast) cells, and .beta.-1,4 bonds in mixed .beta.-1,3-1,4-glucans such as cereal .beta.-D-glucans. The authorized systematic name is 1,3-(1,3;1,4)-.beta.-D-glucan 3(4)-glucanohydrolase, and the common name is Laminarinase, but the abbreviated term endo-1,3(4)-.beta.-glucanase is used in the present specification.
Cell walls of fungal microorganisms such as yeasts and fungi are complex structures which, in addition to .beta.-glucan, comprise a number of other components. For instance, yeast cell walls comprise a protein-mannan complex layer in addition to a glucan layer (Andrews and Asenjo, 1987), and cell walls of filamentous fungi additionally comprise varying amounts of chitin and chitosan (cf. Hudson, H. J., 1986).
It is well-known that microorganisms produce a number of valuable products such as colorants, flavourants, vitamins, the isolation of which is desirable. The isolation of intracellularly produced products requires that the cell walls of the microbial producers be ruptured or lysed.
Because of the complex composition of microbial cell walls, the rupture or lysis of cell walls has traditionally been carried out by rather vigorous treatments involving the use of strong chemicals and/or mechanical means.
Enzymatic lysis and disruption of microbial cells have been suggested as a desirable alternative to chemical or mechanical rupture in the production of yeast extracts or other intracellulary produced products (Andrew and Asenjo (1987); Phaff (1977)). Furthermore, enzymatic lysis has been suggested for use in the preparation of protoplast from fungi or yeasts (Hamlyn et al., 1981). A number of commercially available enzyme preparations useful in the enzymatic lysis of yeast and fungal cells are available. Such products normally comprise multiple enzymatic activities, e.g. including .beta.-1,3- and/or .beta.1,6-glucanase, protease, chitinase, mannanase and other enzymes capable of cleaving cell wall components.
According to Pitson et al., (1993), filamentous fungi such as Rhizopus arrhizus, Trichoderma longibranchiatum and Penicillum funiculosium are known to produce enzymes exhibiting endo-1,3(4)-.beta.-glucanase activity.
The object of the invention is to provide a novel endo-.beta.-glucanase and a method for producing the endo-.beta.-glucanase in a better yield and higher purity than hitherto possible, as well as the use of the endo-1,3(4)-.beta.-glucanase either alone or in combination with other enzymes for the degradation of plant or microbial cell wall tissue. Also it is the object of the invention to provide novel products, wherein the proportion of the endo-1,3(4)-.beta.-glucanase is increased relative to the proportion of the original product.
It would be desirable to be able to improve the cell wall degrading or modifying capability of such enzyme preparations and further to be able to more specifically control the degradation or modification of specific plant or microbial cell wall components.